Why is my Try/Except block in my add_to_list function still giving me a ValueError?

import os
shopping_list = []

def clear_screen():
    os.system("cls" if os.name =="nt" else "clear")

def num_items(shopping_list):
    print ("List has {} items.".format(len(shopping_list)))

def add_to_list(item):
    if len(shopping_list):
        position = int(input("Where are we putting {}?\n  ".format(item)))    
    else:
        position = 0
    try:
        position = abs(int(position))
    except ValueError:
        position = None

    if position is not None:
        shopping_list.insert(position - 1, item)
    else:
        shopping_list.append(new_item)
    show_list(shopping_list)



def remove_item(item):
    item = input("Which item would you like to remove?  ")
    item = item.upper()
    shopping_list.remove(item)

def show_help():
    clear_screen()
    print("What should we get at the store?")
    print("""
Enter 'DONE' to stop adding items.
Enter 'HELP' to show this menu.
Enter 'SHOW' to show list.
Enter 'REMOVE' to remove items
Enter 'CLEAR' to clear the list
""") 
    show_list(shopping_list)


def show_list(shopping_list):
    clear_screen()
    print ("List has {} items.".format(len(shopping_list))) 
    index = 1
    for item in shopping_list:
        print ("{}. ".format(index) +item)
        index += 1        
    print ("-"*10)    

def clear_list(shopping_list):
    while len(shopping_list) > 0:
            for item in shopping_list:
                shopping_list.remove(item)
                show_list(shopping_list)

#THIS IS THE LOGIC 
show_help()
while True:
    new_item = input("> ")
    if new_item.upper() == 'DONE' or new_item.upper() == 'QUIT':
        show_list(shopping_list)
        break
    elif new_item.upper() == 'HELP':
        show_help()
        continue
    elif new_item.upper() == 'SHOW':
        show_list(shopping_list)
        continue
    elif new_item.upper() == 'REMOVE': 
        remove_item(new_item)
        show_list(shopping_list)
    elif new_item.upper() == 'CLEAR':
        clear_list(shopping_list)
        continue        
    else:
        new_item = new_item.upper()
        add_to_list(new_item)